Flexible solid-state conductors

ABSTRACT

Various embodiments of solid-state conductors containing solid polymer electrolytes, electronic devices incorporating the solid-sate conductors, and associated methods of manufacturing are described herein. In one embodiment, a solid-state conductor includes poly(ethylene oxide) having molecules with a molecular weight of about 200 to about 8×10 6  gram/mol, and a soy protein product mixed with the poly oxide), the soy protein product containing glycinin and β-conglycinin and having a fine-stranded network structure. Individual molecules of the poly(ethylene oxide) are entangled in the fine-stranded network structure of die soy protein product, and the poly(ethylene oxide) is at least amorphous.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to U.S. Provisional Application No.61/483,829 filed on May 9, 2011, the contents of which are incorporatedherein by reference.

BACKGROUND

Requirements for increasing energy storage continue to grow. Nextgeneration microelectronics demand a multitude of high performancebattery products including flexible batteries, clean power forautomobiles etc., and all will depend on new battery technology forlonger cycle life, higher energy densities, better recharge ability andincreased reliability. In addition, there will always be anenvironmental concern during production and use regarding safety andrecycling. Further, since electrolytes in a battery conduct the ions,block electrons, and separate the electrodes to prevent shorting, theelectrolytes are an important part of a battery, and the development ofhigh performance “green” solid electrolytes will be significant forefficient battery technology, enhancement and broad applications.

Flexible electronic devices have certain functional advantages. Forexample, a flexible digital display may be used to output informationfrom a computer, and then rolled up to save space when not in use. Inanother example, flexible solar cells have been developed far poweringsatellites. Such solar cells may be rolled up for launch, and are easilydeployable when in orbit. Despite such functional advantages,conventional flexible electronic devices are typically externallypowered because flexible batteries are not readily available. Onechallenge of producing flexible batteries is a lack of high qualitysolid-state conductors with good compliance or flexibility.

SUMMARY

This disclosure is not limited to the particular systems, devices andmethods described, as these may vary. The terminology used in thedescription is for the purpose of describing the particular versions orembodiments only, and is not intended to limit the scope.

In one embodiment, a solid state conductor is provided, comprising atleast one polymer comprising a polyether; and at lest one proteinproduct mixed with the polymer, wherein the protein product has afine-stranded network structure; wherein individual molecules of thepolyether are entangled in the fine-stranded network structure of theprotein product such that the polyether molecules are at least about 50%amorphous.

In an alternative embodiment, an electronic device is provided,comprising a first electrode; a second electrode spaced apart from thefirst electrode; a solid polymer electrolyte disposed between the firstelectrode and second electrode, the solid polymer electrolyte having aflexibility of about 50% to about 700% and comprising: a plurality ofpolyether molecules: and at least one protein product mixed with thepolyether molecules, the protein product having a plurality of proteinstrands in a fine-stranded network structure, wherein individualmolecules of the polyether are entangled in the fine-stranded networkstructure of the protein product: wherein the solid polymer electrolyte,has an electrical conductivity that allows an electrical current to flowbetween the first electrode and second electrode.

In an additional embodiment, a method for preparing a solid-stateconductor is provided. The method can comprise providing a proteindispersion of a protein in as solvent; mixing a polyether material withthe protein dispersion to form a polyether-protein mixture; andevaporating the solvent from the polyether-protein mixture to form thesolid-state conductor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic diagrams of an electronic device duringvarious operating modes in accordance with embodiments of the presenttechnology.

FIG. 1C shows chemical structures and perspective views of a solid-stateconductor suitable for the electronic device in FIGS. 1A and 1B inaccordance with embodiments of the technology.

FIG. 2 is a flowchart showing a method of manufacturing a solid-stateconductor suitable for the electronic device of FIGS. 1A and 1B inaccordance with embodiments of the technology.

FIG. 3A shows a series of four photographs of tensile tests performed ona solid-state conductor prepared according to embodiments of the methodin FIG. 2.

FIG. 3B shows a plot of load in μN (y-axis) vs. depth in nm (x-axis).The p-SPE film is indicated with solid lines, while the s-SPE film isindicated with dashed lines.

FIG. 3C shows impedance spectra obtained for the p-SPE film (squaresymbols). The x-axis is Z_(p)/10⁴ (ohms), with a scale of 0-14, They-axis is Z_(i)/10⁴ (ohms), with a scale of 0-50. The bulk resistance isindicated as R_(b).

FIG. 3D shows impedance spectra obtained for the s-SPE film (roundsymbols). The x-axis is Z_(q)/10⁴ (ohms), with a scale of 0-1. They-axis is Z_(i)/10⁴ (ohms), with a scale of 0-10, The bulk resistance isindicated as R_(b).

FIG. 3E is a bar graph with the x-axis being various material loaded tothe PEO/LiClO₄and the y-axis being conductivity enhancement times with ascale of 0-120.

FIG. 3F is a plot of log (frequency/Hz) (x-axis; scale of 1-7) againstlog (conductivity/S cm⁻¹) (y-axis; scale of −8 to −3). The squaresymbols represent as-received s-SPE film; the round symbols represent100% stretched s-SPE film; and the diamond symbols represent retracteds-SPE film.

FIG. 4 shows an example conductivity versus frequency plot for asolid-state conductor prepared according to embodiments of the method inFIG. 2. The x-axis is frequency (Hz), and the y-axis is conductivity(S/cm).

DETAILED DESCRIPTION

Various embodiments of solid-state conductors containing solid polymerelectrolytes (“SPEs”), electronic devices incorporating the solid-sateconductors, and associated methods of manufacturing are described below.The term “solid polymer electrolyte” or “SPE” is used throughout torefer to a solid polymer material that is capable of transporting ionsand/or other charge carriers to effect ionic and/or other types ofconductivity, collectively referred to herein as “electricalconductivity”). A person skilled in the relevant art will alsounderstand that the technology may have additional embodiments, and thatthe technology may be practiced without several of the details of theembodiments described below with reference to FIGS. 1A-4.

Solid polymer electrolytes (SPEs) that possess high ionic conductivityand attractive mechanical compliance are in great demand for a broadrange of electronic and power applications. Though the initial work hasconcentrated on their function in lithium ion batteries, applicationsnow also may include chemical sensors, organic thin film transistors,electromechanical actuators, polymer light emitting electrochemicalcells, and gas separation membranes. For some applications of SPEs, itis desirable to incorporate high ionic conductivity while maintainingthe mechanical properties. Further, for additional applications of SPEs,it may be desirable for SPEs to possess both high ionic conductivity andalso high elasticity, which is required to make thin and flexibledevices for the next generation electronics and high power densityapplications.

Highly flexible and conductive SPEs may also be usable for stretchableartificial skins for humans. Such skins are commercially available, butthey lack electric functionality. Various stretchable materials, such asrubber, are used in daily activities, but they have poor electricproperties. For some artificial skin applications it may be desirablethat the skin include stretchable active electronic elements andinterconnects. A power sources may be needed for the operation of theskin-like sensitivity, and ideally, a power source directly integratedonto the skin would preferred for easy system integrations.

Highly flexible and conductive SPEs are needed for foldable/flexibledevices in high power density applications. It is believed that neitheran elastomer blended poly(ethylene oxide) (PEO), nor a “polymer in salt”reached an acceptable electrical conductivity at room temperatures.Developing high performance SPEs using a bio-material can be alsochallenging. Protein, such as soy protein, is one of the most abundantrenewable resources. However, soy protein products may he rigid and maylead to poor processability and brittleness for polymer blends. Forexample, strain of poly(ester urethane) film decreased from 750% to lessthan 50% after addition of 20 wt % of soy protein isolate (SPI).However, it has been discovered that by blending protein, such as SPIwith polyether, such PEO, a highly flexible protein-based SPE (s-SPE)with high electrical conductivity may produced.

SPEs based on PEO have certain advantages: (1) possible to produce thinfilms of large surface areas, (2) flexibility in designs, (3) nocorrosive or powerful solvents, and (4) batteries or other electricaldevices produced may be packaged in low-pressure containers. However,PEG-based SPEs have rarely found commercial success due to low ionicconductivity and/or insufficient mechanical properties. Both of theseproperties are believed to be related to movement of polymer chains. Forexample, high chain mobility within a polymer lead to high ionicconductivity but can lead to reduced mechanical properties at the sametime. Thus, enhancements in both properties are usually in conflict.Many physical/chemical method have been exploited to create enhancementin both ionic conductivity and mechanical properties. Though somesuggested techniques have shown promise, the complex strategies involvedhave introduced other challenging issues.

In several embodiments of the present technology, a bio-polymer iscombined with a polymer to form SPE materials suitable as solid-stateconductors. The bio-polymer may contain a protein product. The polymermay contain a polyether. The formed SPE materials have a generally aamorphous structure that can enhance ionic conductivity. While providingadequate flexibility and other mechanical properties for fabrication andhandling. In several examples discussed below, SPI is used as an examplebio-polymer to be combined with an example polymer, PEO, to prepareexample SPE materials. While SPI is used as an example bio-polymer,other bio-polymers, proteins, or mixtures of two or more proteins orbio-polymers may similarly he used. Based on experiments conducted, theSPE materials have desirable properties such as high ionic conductivity,good thermal properties, high cation transference number,electrochemical stability, and stable electrolyte-electrode interfacefor batteries. In particular, the flexibility of the SPE materials mayhe controlled by adjusting a denatured structure of the soy protein.Moreover, the SPE materials may be easy to fabricate, and may beconsidered environmentally friendly in both processing and materialusage.

FIGS. 1A-1B are schematic diagrams of an electronic device duringvarious operating modes in accordance with embodiments of the presenttechnology. For illustration purposes, the electronic device isdescribed below using a lithium-ion battery 100 as an example. FIG. 1Ashows the lithium-ion battery 100 during discharging, and FIG. 1B showsthe lithium-ion battery 100 during charging. In other embodiments, theelectronic device can be configured as other types of battery containingsodium, potassium, calcium, magnesium, cadmium, or copper ions, achemical sensor, an organic thin film transistor, an electromechanicalactuator, a polymer light emitting diode, gas separation membrane, afuel cell, and/or other suitable electronic devices.

As shown in FIGS. 1A and 1B, the lithium-ion battery 100 may include ahousing 102 holding a first electrode 104, a second electrode 106, andan SPE 108 between the first and second electrodes 104 and 106. Thelithium-ion battery 100 can also include salts such as LiPF₆LiAsF₆,LiClO₄, LiBF ₄, and lithium triflate contained in the SPE 108.

In certain embodiments, the SPE 108 can include a polymer and a proteinproduct mixed with the polymer. Additional details of the compositionand molecular structure of the SPI 108 are discussed below with respectto FIG. 1C. Even though particular components are illustrated in FIGS.1A and 1B, in other embodiments, the lithium-ion battery 100 can alsoinclude insulators, gaskets, vent holes, and/or other suitablecomponents (not shown).

In one embodiment, the first electrode 104 can include a carbonaceousmaterial (e.g., graphite) tin (Sn), zinc (Zn), lead (Pb), antimony (Sb),bismuth (Bi), silver (Ag), gold (Au), and/or other elementelectrodeposited on and alloy with lithium (Li), or combinationsthereof. In another embodiment, the first electrode 104 can also includea binary, ternary, or higher order mixtures of the elements that can beelectrodeposited on and alloy with lithium (Li). Examples of binarymixtures include Sn—Zn, Sn—Au, Sn—Sb, Sn—Pb, Zn—Ag, Sb—Ag, Au—Sb, Sb—Zn,Zn—Bi Zn—Au, and combinations thereof. Examples of ternary mixturesinclude Sn—Zn—Sb, Sn—Zn—Bi, Sn—Zn—Ag, Sn—Sb—Bi, Sb—Zn—Ag, Sb—Zn—Au,Sb—Sn—Bi, and combinations thereof. An example of a quaternary mixturecan include Sn—Zn—Sb—Bi. In yet another embodiments, the first electrode104 can include intermetallic compounds of elements (e.g., the generallypure elements discussed above) and other elements that can be includeSn—Cu, Sn—Co, Sn—Fe, Sn—Ni, Sn—Mn, Sb—In, Sb—Co, Sb—Ni, Sb—Cu, Zn—Co,Zn—Cu, Zn—Ni, and combinations thereof.

The second electrode 106 can be constructed from a layered oxide (e,g.,lithium cobalt oxide (LiCoO₂)), a polyanion (e,g., lithium ironphosphate (LiFePO₄)), or a spinel (e.g., lithium manganese oxide(LiMn₂O₄. Other suitable materials for the second electrode 106 caninclude lithium nickel oxide (LiNiO₂), lithium iron phosphate fluoride(Li₂FePO₄F), lithium cobalt nickel manganese oxide(LiCo_(1/3)Ni_(1/3)Mn_(1/3)O₂), Li(Li_(a)Ni_(x)Mn_(y)Co_(z))O₂,combinations thereof, and/or other suitable cathode materials.

As shown in FIG. 1A, during discharging, lithium ions 112 are extractedfrom the first electrode 104 and migrate toward the second electrode 106via the SPE 108. The lithium ions 112 pass through the SPE 108 and areinserted into the second electrode 106. As a result, a current 114 flowsfrom the second electrode 106 past a load 116 to the first electrode104. As shown in FIG. 1B, during charging, a charger 118 provides acharging current 120 to the second electrode 106. The charging current120 causes lithium ions 112 to he extracted from the second electrode106 and move toward the first electrode 104.

In an embodiment, such a flexible and conductive SPE may be incorporatedinto an artificial skin to provide the artificial skin with electricalfunctionality. A bio-polymeric, elastomeric, ionic conductive SPE filmmay be configured as a battery in a manner similar to that of FIGS. 1Aand 1B, and may be integrated as a layer with an artificial skin to forma single sheet. An SPE film formed in the manner as discussed herein maybe configured to feel and look like real skin, and can have similarflexibility characteristics as does real skin.

FIG. 1C shows chemical structures and schematic perspective views of anSPE and constituents in accordance with embodiments of the technology.As discussed above, the SPE can include a polymer and as bio-polymercontaining protein product mixed with the polymer. In certainembodiments, the polymer can include a polyether with one or more etherfunctional groups (—C—O—C—). One example of polyether is PEO having amolecular weight of about 200 to about 8×10⁶ gram/mol. Other Examples ofpolyether can include polyethylene glycol (PEG), polyoxyethylene (POE),polypropylene oxide, other oligomer or polymer of ethylene oxide, and/orderivatives thereof. In other embodiments, the polymer can includepolyamines, polyamides, polyketones and/or other suitable polymers withrep eating carbonyl (—C═O), carboxyl (—COOH), hydroxyl (—OH), amino(—NH3), and/or other suitable polar functional groups.

The protein product can include an extract or isolate from plants orother natural resources, a purified protein, or can include asynthesized substance. For example, in certain embodiments, the proteinproduct can include a soy protein product containing glycinin andβ-conglycinin. Examples of such soy protein product can include a soyfood with about 6% to about 50% soy protein, a soy flour with about 50%to about 80% soy protein, a soy meal with about 80% to about 90% soyprotein, and an SPI with about 90% soy protein or higher. In otherembodiments, the protein productalso include a protein product derivedfrom peanuts, almonds, milk, black beans, sunflower seeds, wheat, rice,and/or other ot.laer suitable plants or plant products.

In certain embodiments, a ratio of the soy protein product to the PEOcan be about 20:80 by weight to about 60:40 by weight. For example, inone embodiment, a ratio of the soy protein product to the PEO is about25:75. In another embodiment, a ratio of the soy protein product to thePEO is about 30:70. In another embodiment, a ratio of the soy proteinproduct to the PEO is about 35:65. In another embodiment, a ration ofthe soy protein product to PEO is about 40:60. In another embodiment, asratio of the soy protein product to the PEO is about 45:55. In anotherembodiment, as ratio of the soy protein product to the PEO is about50:50. In yet another embodiment, a ratio of the soy protein product tothe PEO is about 55:45. In further embodiments, the ratio of the soyprotein product to the PEO can have other suitable values.

The protein product can contain a plurality of protein strands in afine-stranded network structure. As used herein, the term“fine-stranded” generally refers to a structural feature in whichindividual strands are at last partially unfolded in a thread or athreadlike configuration. Without being bound by theory, it is believedthat proteins extracted from plants or plant products are typicallyfolded into a globular or fibrous foam. For example, as shown in part(a) in FIG. 1C, glycinin in SPI has one basic and acidic polypeptide,which are linked to each other by a single disulfide bond. β-conglycininis a trimeric glycoprotein including three types of subunits α,α′, andβ, in seven different combinations. The subunits are believed to beassociated through hydrophobic anti hydrogen bonding, which can causethe protein strands to have a coil-like structure 130.

A process generally referred to as “denaturation” may be performed to atleast partially unfold the protein strands in order to form thefine-stranded network structure. Denaturation may be done by heating adispersion of the protein product in solution, changing the pH of theprotein product solution, adding denaturing agents such as urea and(guanidine hydrochloride, or via other suitable techniques andcombinations of the techniques. During denaturation, the bondinginteractions responsible for the secondary and tertiary structures inprotein strands may be disrupted, resulting in an unfolding of thecoiled structure 130 and leading to a fine-stranded network structurewith unfolded strands 132, as shown in part (b) of FIG. 1C. Also shownin part (b) of FIG. 1C, ions (e.g., lithium ions) 134, which in at leastsome embodiments may be provided by various salts, can be stronglyadsorbed onto the surf of the soy protein product due to the negativeacid group in the SPI. Thus, a preferential protein-salt binding resultsin effective protein-protein repulsion. As a result, as used herein,“denaturation” generally refers to any modification of secondary,tertiary, or quaternary structure of protein molecules generally withoutbreaking covalent bonds. The pH can generally be any pH. In someembodiments, the pH is greater than 7 (basic). For example, the pH canbe about 7, about 8, about 9, about 10. about 11, about 12, about 13,about 14, and ranges between any two of these values (such as about 10to about 11).

Some examples of salts which may be included in embodiments of SPEsalong with the protein and the polymer, may include, but are not limitedto, LiPF₆, LiTFSI, LiBF₄, LiClO₄, LiN(CF₃SO₂)₂, LiAsF₆, LiCF₃SO₃, LiI,LiBC₄O₈(LiBOB), Li[PF₃(C₂F₅)₃], LiTf, Lilm, LiBr, LiCl, LiSCN, LiTFSM,NaI, LiCF₃CO₂ NaBr, NaSCN, KSCN, MgCl₂, Mg(ClO₄)₂. The amount of thesalt that is included may range from about 1% to about 45%, and may beabout 1%, about 5%, about 10%, about 15%, about 20%, about 25%, about30%, about 35%, about 40%, about 45%, or any amount between any two ofthese values, or art other suitable amount.

In an exemplary embodiment wherein the sarlt a be about 10 wt % to about25 wt % of the SPE, and a ratio of the protein product to the polymermay be about 45:55, the weight percentages of the protein and thepolymer may be about 33 wt % to about 40 wt % protein and about 41 wt %to about 49 wt % polymer. In another exemplary embodiment, wherein thesalt may be about 10 wt % to about 25 wt % of the SPE, and to ratio ofthe protein product to the polymermay be about 50:50, the weightpercentages of the protein and the polymer nay both be about 37 wt % toabout 45 wt %. hn yet another exemplary embodiment, wherein the salt maybe about 10 wt % to about 25 wt % of the SPE, and a ratio of the proteinproduct to the polymer may be about 55:45, the weight percentages of theprotein and the polymer may be about 41 wt % to about 49 wt % proteinand about 33 wt % to about 40 wt % polymer.

As shown in part (c) of FIG. 1C, the PEO molecules 136 are entangled inthe fine-stranded network structure of the protein product. The SPIprotein strands are surrounded by the PEO molecules 136 having aconfiguraton, rather than making a protein-protein contact. The“electron-rich” sites in the PEO molecules 136 are absorbed to lithiumions or bonded to a positive ammonium group of the protein strands 132.The foregoing structural features highly disturb the carder of the PEOmolecule 136, resulting in a highly amorphous structure. At the sametime, the cross-linking or entanaglements between PEO and SPI contributeto high mechanical flexibility, for example, about 50% to about 700%. Asused herein, the term “flexibility” generally refers to a percentage ofdeformation at which a material can return to an original dimension andshape within certain tolerances about 5%, about 10%, about 15%, or othersuitable percentage values) generally without damaee.

Even though the SPE is described above as being based on a mixture ofPEO and SPI containing a lithium salt, in other embodiments, the SPE mayinclude other suitable polymers, salts, and/or bio-polymer productshaving the structures and functional groups described below. In furtherembodiments, the SPE can also include a filler material, a stiffenermaterial, a carrier material, and/or other suitable materials. Inaddition, the SPE may be formed as a film, a block, a pellet, and/orother suitable geometric configurations.

FIG. 2 is a flowchart showing a method of manufacturing to solid-stateconductor suitable for the electronic device of FIGS. 1A and 1B inaccordance with embodiments of the technology. As shown in FIG. 2, stage202 of the method can include adding at protein product to at solutionor solvent to form at protein dispersion. The solvent can generally beany solvent, such as an aqueous solvent or a non-aqueous solvent. Thesolvent can be a single solvent or a co-solvent combination of two ormore solvents (such as water with an alcohol such as methanol orethanol.). In some examples, the solvent is water. In other examples,the solvent is water with one or more dissolved substances (such assalts, buffers, acids, bases, and so on). The method also includesdenaturing, the protein product in the protein dispersion at stage 204.As discussed above, in certain embodiments, the protein product can bedenatured by heating the protein dispersion at a pH and temperature fora target period of time. In other embodiments, the protein product canalso be denatured by sonication, radiation, and/or other suitabletechnique. Subsequently, a polymer can be dissolved in the proteindispersion at stage 206 to form a polymer-protein mixture. Thepolymer-protein mixture can then be casted, spray dried, baked, and/orotherwise processed to form the solid-state conduct at stage 208.

As shown in FIG. 2, the method can optionally further include adjustingat least one of the pH of the solvent, the treatment temperature, thetreatment period, or other suitable denaturing conditions 210 based onat least one of a target electrical conductivity or a mechanicalflexibility of the solid-state conductor. It is believed that proteinchemistry involves many interactions, including electrostaticinteractions and hydrogen bonding, hydrophobic interactions, covalentbonding, and ionic bonding. Protein structure changes during thedenaturation process to allow interactions between protein and polargroups in the polymer and between the protein and a salt to occur. As aresult, by adjusting art least one of the denaturing conditions, atarget morphology may be obtained. The target morphology may be about50% amorphous, about 60% amorphous, about 70% amorphous, about 80%amorphous, about 90% amorphous, about 95% amorphous, about 100%atrtorphous, ranges between any two of these values.

Several expetimems were performed to produce and test s-SPEs accordingto aspects of the present technology. During these experiments,bio-elastorneric and electrically conductive materials were preparedusing a solution catsttng technique. Protein dispersions were preparedby magnetically stirring appropriate amount of protein (e.g SPI) in 60ml of lithium perchlorate (LiClO₄) solution with pH of about 10 and thensonicating for about 1 hour. The resultant dispersions were heated atabout 95° C. for about 10 hours. Then 1 g of PEO powder was dissolvedinto the above dispersion and the mixture was magnetically agitated.Before casting, the mixture was sonicated for another hour. The mixturewas cast on a smooth polyethylene substrate to let the solventevaporate. Subsequently, an s-SPE film was obtained. Solvent can beevaporated by a variety of methods. Examples include heating, exposingto reduced pressure, ventilation, and passive evaporation.

Elasticity of the s-SPE film was examined by tensile tests andnano-indentation. FIG. 3A is a series of four photographs showing thes-SPE film in a tensile process. The average ultimate tensile strength,σ_(u), was 0.98±0.07 MPa; the elastic modulus (E) was 0.08±0.02 MPa andthe elongation at break is greater than about 740%. In contrast, purePEO based electrolyte (p-SPE) film was too sticky to be peeled off froma substrate without damage. Thus, a nano-indentation approach wasapplied to compare the mechanical properties between s-SPE and p-SPE.

FIG. 3B shows that the s-SPE film was much more elastic than the p-SPEfilm. FIG. 3B shows a plot of load in μN (y-axis) vs. depth in mm(x-axis), where movement down and towards the right indicate moreelasticity. The p-SPE film is indicated with solid lines, while thes-SPE film is indicated with dashed lines. Without being bound bytheory, it is believed that the high flexibility of the s-SPE film isrelated to the micro-structures thereof. Distinct spherulites werevisible in the p-SPE film using polarized optical images. With theaddition of denatured SPI, no spherulites were observed, which indicateda near amorphous state of the s-SPE film. Results of mechanical testsare shown in the table below.

Ultimate Stress Strain at breaking Sample (MPa) Modulus (MPa) point (%)p-SPE 0.31 ± 0.05 14.50 ± 6.45 305.50 ± 208.42 s-SPE 0.98 ± 0.53  0.06 ±4.42 742.62 ± 11.53 

FIGS. 3C and 3D show impedance spectra obtained, for the p-SPE film(FIG. 3C; square symbols) and s-SPE film (FIG. 3D; round symbols). Thebulk resistance (Rb) of the s-SPE film (about 0.1) was significantlyreduced compared to that of the p-SPE film (about 10.5). Thus, asignificant enhancement in electrical conductivity was observed in thes-SPE film when compared to the p-SPE film. Without being bound bytheory, it is believed that such an enhancement was due to increases inboth charge carriers and ion mobility. For example, soy proteinmolecules with a helical structure typically include a large amount ofpolar functional groups. After denaturation, the folded proteinstructure was transformed to an unfolded threadlike configuration, whichfavors lithium salt dissociation. The amorphous state of the s-SPE filmaccommodates a high degree of polymer segment mobility above T_(g)(e.g., −40° C.) to provide a favorable environment for iontransportation.

FIG. 3E shows a bar graph comparison of reported conductivity results ofPEO nano-composites with nanoparticles (such as Al₂O₃, SiO₂, andpolyhedral oligomeric silsesquioxanes (POSS)) and polymer blend(poly(ε-caprolactone) added into PEO (PCL)), against the s-SPE film(SPI). The conductivity results for the materials other than SPI wereobtained front reported literatures. The conductivity enhancement withthe s-SPE film was at least about eighty times higher than othertechniques.

FIG. 3F shows frequency dependent ionic conductivity of the as-received,stretched, and retracted s-SPE film. The square symbols representas-received s-SPE film; the round symbols (upper line) represent 100%stretched s-SPE film: and the triangle symbols (substantially thebottom-most line) represent retracted s-SPE film. As shown in FIG. 3F,the s-SPE film was elongated up to 100% and relaxed without loss ofionic conductivity, as the lines for the as-received and retracted films(bottom pair of lines) essentially overlap.

FIG. 4 shows an example conductivity versus frequency plot for a PEOfilm and the s-SPE film prepared according to embodiments of the methodin FIG. 2. The concentration of LiClO₄ in both materials was about 22 wt%. As shown in FIG. 4, the conductivity of the two materials increasedwith increasing frequency. In the SPI/PEO/LiClO₄ system (upper curve;round symbols), the conductivity values increased two orders highercompared with that without SPI (lower curve square symbols). Withoutbeing bound by theory, it is believed that conductivity in SPEs, themotion of cations and anions and the number of mobile charges areaffected by the interactions between the salt and the polar matrix. Suchinteractions include hydrogen bonding, dipole-dipole, ion-dipole, chargetransfer or transition metal complexation. Denatured SPI can have manypolar groups, thus the addition of SPI is believed to facilitatedissociation of lithium salt. As a result, the number of the free chargecarriers increased.

From the foregoing, it will be appreciated that specific embodiments ofthe disclosure have been described herein for purposes of illustration,but that various modifications may be made without deviating from thedisclosure. In addition, many of the elements of one embodiment may becombined with other embodiments in addition to or in lieu of theelements of the other embodiments. Accordingly, the technology is notlimited except as by the appended claims.

This disclosure is not limited to the particular systems, devices andmethods described, as these may vary. The terminology used in thedescription is for the purpose of describing the particular versions orembodiments only, and is not intended to limit the scope.

In the above detailed description, reference is made to the accompanyingdrawings, which form a part hereof. In the drawings, similar symbolstypically identify similar components, unless context dictatesotherwise. The illustrative embodiments described in the detaileddescription, drawings, and claims are not meant to he limiting. Otherembodiments may be used, and other changes may be made, withoutdeparting from the spirit or scope of the subject matter presentedherein. It will be readily understood that the aspects of the presentdisclosure, as generally described herein, and illustrated in theFigures, can be arranged, substituted, combined, separated, and designedin a wide variety of different configurations, all of which areexplicitly contemplated herein.

The present disclosure is not to be limited in terms of the particularembodiments described in this application, which are intended asillustrations of various aspects. Many modifications and variations canbe made without departing from its spirit and scope, as will be apparentto those skilled in the art. Functionally equivalent methods andapparatuses within the scope of the disclosure, in addition to thoseenumerated herein, will be apparent to those skilled in the art from theforegoing descriptions. Such modifications and variations are intendedto fall within the scope of the appended claims. The present disclosureis to be limited only by the terms of the appended claims, along withthe full scope of equivalents to which such claims are entitled. It isto be understood that this disclosure is not limited to particularmethods, reagents, compounds, composition or logical systems, which can,of course, vary. It is also to be understood that the terminology usedherein is for the purpose of describing particular embodiments only, andis not intended to be limiting.

As used in this document, the singular forms “a,” “an,” and “the”include plural references unless the context clearly dictates otherwise.Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of ordinary skillin the art. Nothing in this disclosure is to be construed as anadmission that the embodiments described in this disclosure are notentitled to antedate such disclosure by virtue of prior invention. Asused in this document, the term “comprising” means “including, but notlimited to.”

While various compositions, methods, and devices are described in termsof “comprising” various components or steps (interpreted as meaning“including, but not limited to”), the compositions, methods, and devicescan also“consist essentially of” or “consist of” the various componentsand steps, and such terminology should be interpreted as definingessentially closed-member groups.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to embodiments containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should he interpreted to mean “at least one”or “one or more”); the same holds true for the use of definite articlesused to introduce claim recitations. In addition, even if a specificnumber of an introduced claim recitation is explicitly recited, thoseskilled in the art will recognize that such recitation should beinterpreted to mean at least the recited number (e.g., the barerecitation of “two recitations,” without other modifiers, means at leasttwo recitations, or two or more recitations). Furthermore, in thoseinstances where a convention analogous to “at least one of A, B, and C,etc.” is used, in general such a construction is intended in the senseone having skill in the art would understand the convention (e.g.,“asystem having at least one of A, B, and C” would include but not helimited to systems that have A alone, B alone, C alone, A and Btogether, A and C together, B and C together, and/or A, B, and Ctogether, etc.). In those instances where a convention analogous to “atleast one of A, B, or C, etc.” is used, in general such as constructionis intended in the sense one having skill in the art would understandthe convention (e.g., “a system having at least one at A, B, or C” wouldinclude but not be limited to systems that have A alone B alone, Calone, A and B together, A and C together, B and C together, and/or A,B, and C together, etc.). It will be further understood by those withinthe art that virtually any disjunctive word and/or phrase presenting twoor more alternative terms, whether in the description, claims, ordrawings, should be understood to contemplate the possibilities ofincluding one of the terms, either of the terms, or both terms. Forexample, the phrase “A or B” will be understood to include thepossibilities of “A” or “B” or “A and B.”

In addition, where features aspects of disclosure are described in termsMarkush groups, those skilled in the art will recognize that thedisclosure is also thereby described in terms of any individual memberor subgroup of members of the Markush group.

As will be understood by one skilled in the art, for any and allpurposes, such as in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc. As will also be understood by one skilled in the art all languagesuch as “up to,” “at least,” and the like include the number recited andrefer to ranges which can be subsequently broken down into subranges asdiscussed above. Finally, as will be understood by one skilled in theart, a range includes each individual member. Thus, for example, a grouphaving 1-3 cells refers to groups having 1, 2, or 3 cells. Similarly, agroup having 1-5 cells refers to groups having 1, 2, 3, 4, or 5 cells,and so forth.

Various of the above-disclosed and other features and functions, oralternatives thereof, may be combined into many other different systemsor applications. Various presently unforeseen or unanticipatedalternatives, modifications, variations or improvements therein may besubsequently made by those skilled in the art, each of which is alsointended to be encompassed by the disclosed embodiments.

1. A solid-state conductor, comprising: at least one polymer comprisinga polyether; and at least one protein mixed with the polymer, whereinthe protein product has a fine-stranded network structure; whereinindividual molecules of the polyether are entangled in the fine-strandednetwork structure of the protein such that the polyether molecules areat least about 50% amorphous.
 2. The solid-state conductor of claim 1,wherein the polyether comprises a polymer of alkylene oxide.
 3. Thesolid-state conductor of claim 1, wherein the polyether comprisespoly(ethylene oxide), polyoxyethylene, poly(propylene oxide), or acombination thereof.
 4. The solid-state conductor of claim 1, whereinthe polyether is poly(ethylene oxide) having a molecular weight of about200 to about 8×10⁶ gram/mol.
 5. (canceled)
 6. The solid-state conductorof claim 1, wherein the polymer comprises polyamines, polyamides,polyketones, polycarbonate, polyimine, polyester, polyurethane, or acombination thereof. 7.-8. (canceled)
 9. The solid-state conductor ofclaim 1, wherein the protein comprises glycinin, β-conglycinin, or acombination thereof.
 10. The solid-state conductor of claim 1, furthercomprising at least one salt.
 11. The solid-state conductor of claim 1,further comprising a plurality of cations noncovalently bound with thepolyether, the protein, or both.
 12. The solid-state conductor of claim11, wherein the cation comprises Li⁺, K⁺, Na⁺, Ca²⁺, Mg²⁺, Cd²⁺, Al³⁺,Zn^(2′), Fe²⁺, Fe³⁺, Pb²⁺, Cu²⁺, Ag⁺, or a combination thereof. 13.(canceled)
 14. The solid-state conductor of claim 1, wherein a ratio ofthe protein polymer to the polyether is about 20:80 by weight to about60:40 by weight.
 15. (canceled)
 16. The solid-state conductor of claim1, wherein: a ratio of the protein to the polyether is about 55:45 byweight; the polyether molecules are about 100% amorphous; and thepolyether mixed with the protein have a flexibility of about 50% toabout 700%. 17.-19. (canceled)
 20. The solid state conductor of claim10, wherein the at least one salt comprises at least one of LiPF₆,LiTFSI, LiBF₄, LiClO₄, LiN(CF₃SO₂)₂, LiAsF₆, LiCF₃SO₃, LiI,LiBC₄O₈(LiBOB), Li[PF₃(C₂F₅)₃], LiTf, Lilm, LiBr, LiCl, LiSCN, LiTFSM,NaI, LiCF₃CO₂, NaBr, NaSCN, KSCN, MgCl₂ and Mg(ClO₄).
 21. Thesolid-state conductor of claim 10, wherein: the polymer is poly(ethyleneoxide), the protein is a soy protein and the salt comprises at least oneof LiPF₆, LiTFSI, LiBF₄, LiClO₄, LiN(CF₃SO₂)₂, LiAsF₆, LiCF₃SO₃, LiI,LiBC₄O₈(LiBOB), Li[PF₃(C₂F₅)₃], LiTf, Lilm, LiBr, LiCl, LiSCN, LiTFSM,NaI, LiCF₃CO₂, NaBr, NaSCN, KSCN, MgCl₂ and Mg(ClO₄); and the solidstate conductor comprises about 10 wt % to about 25 wt % salt, about 33wt % to about 40 wt % polymer, and about 41 wt % to about 49 wt %protein. 22.-24. (canceled)
 25. An electronic device comprising: a firstelectrode; a second electrode spaced apart from the first electrode; asolid polymer electrolyte disposed between the first electrode andsecond electrode, the solid polymer electrolyte having a flexibility ofabout 50% to about 700% and comprising: a plurality of polyethermolecules; and at least one protein mixed with the polyether molecules,the protein having a plurality of protein strands in a fine-strandednetwork structure, wherein individual molecules of the polyether areentangled in the fine-stranded network structure of the protein; andwherein the solid polymer electrolyte has an electrical conductivitythat allows an electrical current to flow between the first electrodeand second electrode.
 26. The electronic device of claim 25, wherein anoxygen polar group of one of the polyether molecules is bound to anammonium group of one of the protein strands.
 27. The electronic deviceof claim 25, further comprising at least one salt contained in the solidpolymer electrolyte, wherein the solid polymer electrolyte has an ionicconductivity that allows ions of the salt to migrate between the firstelectrode and second electrode.
 28. The electronic device of claim 25,further comprising at least one salt contained in the solid polymerelectrolyte, wherein individual carbonyl groups of one of the proteinstrands are bound to a cation of the salt to effect repulsion fromadjacent protein strands.
 29. (canceled)
 30. The electronic device ofclaim 25, further comprising at least one salt contained in the solidpolymer electrolyte, wherein: at least one of the protein strands has acarbonyl group; at least one of the polyether molecules has a firstoxygen polar group and a second oxygen polar group; a cation of the saltis bound to the first oxygen polar group of the one of the polyethermolecules and to the carbonyl group of the one of the protein strands;and the second oxygen polar group of the polyether molecule is bound toan ammonium group of the protein strand.
 31. A method for preparing asolid-state conductor, the method comprising: providing a proteindispersion of a protein in a solvent; mixing a polyether material withthe protein dispersion to form a polyether-protein mixture; andevaporating the solvent from the polyether-protein mixture to form thesolid-state conductor.
 32. (canceled)
 33. The method of claim 31,wherein: providing a protein dispersion comprises adding the protein toa solvent having a pH to generate the protein dispersion; and the methodfurther comprises: heating the protein dispersion at a treatmenttemperature for a treatment period prior to mixing with a polyethermaterial; and adjusting at least one of the pH of the solvent, thetreatment temperature, or the treatment period based on at least one ofa target electrical conductivity or a targeted mechanical flexibility ofthe solid-state conductor. 34.-38. (canceled)
 39. The method of claim33, wherein: the protein includes a plurality of protein strands in acoiled structure; heating the protein dispersion includes substantiallyunfolding the plurality of protein strands in the coiled structure,thereby forming a fine-stranded network structure with the plurality ofprotein strands; and adjusting at least one of the pH of the solvent,the treatment temperature, or the treatment period includes adjusting atleast one of the pH of the solvent, the treatment temperature, or thetreatment period to substantially unfold the plurality of proteinstrands in the coiled structure.
 40. (canceled)
 41. The method of claim33, wherein: the protein includes a plurality of protein strands;heating the protein dispersion includes forming a fine-stranded networkstructure with the plurality of protein strands; and evaporating thesolvent forms a solid-state conductor having the polyether materialentangled in the fine-stranded network structure of the protein.
 42. Themethod of claim 31, further comprising adjusting at least one of a ratiobetween the polyether material and the protein, a composition of thepolyether material, or a composition of the protein based on at leastone of a target electrical conductivity or a target mechanicalflexibility of the solid-state conductor.
 43. The method of claim 31,wherein the solvent comprises water.
 44. (canceled)
 45. The method ofclaim 31, wherein providing a protein dispersion comprises: dissolving asalt in a solvent to form a salt solution; and mixing a protein with thesalt solution to form the protein dispersion. 46.-48. (canceled)
 49. Themethod of claim 45, wherein: the polyether material comprisespoly(ethylene oxide) the protein comprises a soy protein; the saltcomprises at least one of LiPF₆, LiTFSI, LiBF₄, LiClO₄, LiN(CF₃SO₂)₂,LiAsF₆, LiCF₃SO₃, LiI, LiBC₄O₈(LiBOB), Li[PF₃(C₂F₅)₃], LiTf, Lilm, LiBr,LiCl, LiSCN, LiTFSM, NaI, LiCF₃CO₂, NaBr, NaSCN, KSCN, MgCl₂ andMg(ClO₄); and the solid state conductor comprises about 10 wt % to about25 wt % of the salt, about 33 wt % to about 40 wt % of the poly(ethyleneoxide), and about 41 wt % to about 49 wt % of the soy protein. 50.(canceled)